1. Field of the Invention
The present invention relates to the technical field of a wet-type development method, which is one type of electrophotographic system employed in a printer, a copier, a facsimile device, or a multifunctional apparatus incorporated with the functions of the foregoing devices.
2. Description of the Related Art
Generally speaking, a development method that is adopted in an image forming apparatus using the electrophotographic system which develops an electrostatic latent image with charged colored particles can be broadly classified into a dry-type development method and a wet-type development method depending on the form of the developer. Among the above, the wet-type development method uses a liquid developer in which colored particles are dispersed in an electrically insulating carrier fluid. The colored particles charged in the liquid developer move from a developing roller surface to a photoconductor drum surface based on the principle of electrophoresis, and develop an electrostatic latent image on the photoconductor drum surface. The obtained image is transferred from the photoconductor drum to a recording medium. Since the colored particles in the liquid developer will hardly be scattered into the atmosphere, for example, fine colored particles with an average particle diameter of a submicron size can be used, and a high definition image of high resolution and superior gradation can be obtained.
With an image forming apparatus adopting the electrophotographic system, as a method of fixing the image; that is, the colored particles to the recording medium, known are the heat fixing method and the light fixing method. The heat fixing method is a method of fixing toners to the recording medium by melting a binding resin with heat in cases where the colored particles are toners in which pigments are dispersed in the binding resin. The light fixing method is a method of fixing toners to the recording medium by using a binding resin with a photoreactive functional group as the binding resin, and polymerizing such binding resin with light in cases where the colored particles are toners in which pigments are dispersed in the binding resin. Moreover, it is also known that, by using a specific copolymerized resin and a specific pigment, it is possible to obtain a liquid developer in which are dispersed copolymerized resin particles comprising the pigment with a core part that does not dissolve in an electrically insulated dispersion medium and an outer edge portion which dissolves in the dispersion medium, and that, by using the foregoing liquid developer, it is possible to obtain superior dispersion stability and transfer efficiency without causing any gelling, flocculation, precipitation or the like even if the particle concentration is increased.
Nevertheless, with the foregoing conventional method, it is still necessary to perform a heat-fixing that the resin is melted or dissolved with a high temperature in order to fix the liquid developer including the pigment to the recording paper. In other words, with the heat fixing method and the light fixing method of a wet-type image forming apparatus adopting the conventional wet-type development method, considerable thermal energy or light energy is consumed in order to fix the colored particles to the recording medium.